In InN, a genuine band gap opening observed after hydrogenation has been explained by means of the ``solitary cation'' model, a multi-H complex in which the central cation, In*, is fully separated from the structure .
Similar effects of H on the host band gap have been observed in In-rich InxGaN1-x alloys. Paying attention to these materials, we have theoretically investigated the In* properties against three kinds of disorder, structural, compositional and configurational, all of them possibly
occurring in InxGaN1-x alloys.
As a first, major result we have found that a same, general solitary-cation model and mechanism explain the effects of hydrogenation on the electronic properties of both InN and In-rich InxGaN1-x alloys.
Even more interestingly, in these alloys, both the energetics of the In* solitary cations and their effects on the band gap result to be thoroughly
independent of their atomic neighborhood, in particular, of the number and spatial distribution of their cation neighbors.
Significantly, this implies that band-gap opening effects can be safely predicted in whatever hydrogenated In-rich nitride alloy containing different
In companions (e.g., B, Al, or Ga) as well as in InN-containing, unconventional compounds (e.g., ZnO-InN), thus offering novel opportunities for material engineering.
We used Density Functional Theory (DFT) in the GGA+U approach,[2-3] as implemented with plane wave basis sets in Quantum-ESPRESSO  suite of programs.
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